This invention relates in general to coupling devices, and more particularly to a coupler for connecting a ring gear that is turned by a cranking motor of an internal combustion engine with the crankshaft of the engine for starting the engine.
The conventional automotive engine of the spark ignition type used in automobiles and light trucks, has a relatively heavy flywheel to dampen the torsional pulses imparted by its pistons as those pistons undergo their respective power strokes, and this enables the engine to operate quite smoothly, even when idling at low speeds. While all conventional engines have flywheels which are relatively heavy, the flywheels do not take the same form and vary with the types of transmission through which the engines deliver their power. Where an automatic transmission is used, the housing of the torque converter functions as a flywheel as does the ring gear that is engaged by the starter to crank the engine, the latter being carried by a light plate called a flexplate. On the other hand, where a manual transmission is used, the flywheel assumes a more traditional form. It not only must have enough mass to keep the engine running smoothly at low speeds, but it further must possess sufficient strength to transfer torque to the clutch, for it provides the friction surface against which the clutch plates bear. It also serves as a carrier for the ring gear which the starter engages and in that sense the flywheel used with a manual transmission resembles the flexplate used with an automotive transmission.
Certain high performance engines, such as those used in circle track racing, must have the capacity to accelerate rapidly. They do not require heavy flywheels, because smooth running at idle is sacrificed in favor of acceleration. Aside from that, these engines are rarely equipped with traditional clutches which operate against flywheels. Instead these engines are coupled to their manual transmissions through clutches containing multiple disks of relatively small diameter. Usually the engines used in circle track racing are equipped with the light flexplates identified with automatic transmissions, and then not so much for inertia they provide, but instead as a carrier for the ring gear which the starter engages. In this regard, most promoters of circle track racing open their events only to vehicles having on-board starting. Push starts are not permitted.
But the ring gear on a typical flexplate itself possesses considerable mass--indeed, more than the flexplate itself--and furthermore that mass is concentrated well beyond the axis of rotation. In this regard, the typical ring gear has a diameter 123/4 inches. Thus, the ring gear itself produces a considerable amount of inertia which the engine must overcome to accelerate.
The starter coupler of the present invention carries a ring gear which the pinion of a starting motor engages, and when so engaged the ring gear transmits the torque generated by the starter to the crankshaft of the engine to rotate the same. When the crankshaft of the engine begins to rotate under its own power, the coupler disengages the ring gear from the crankshaft, so that the inertia of the ring gear does not retard acceleration of the crankshaft from a lesser to a greater angular velocity.